Base tablet for sound records



Patented Nov. 18, 1924.

'UNI-TEDSTATES PATENT OFFICE.

some srao'rnna MILLER, an, or nAHwAY, mew JERSEY, AssIoNon To run 3mm ASPHALT COMPANY, or PHILADELPHIA, rnnnsYLvAmA, A conroaArIoN or WEST VIRGINIA.

No Drawing.

To all whom it may concern! Be it known that I, JOHN S'mo'rmm 'MILLER, Jr., a citizen of the United States,

and a resident of Rahway,'in the county of Union and State of New Jersey, have invented certain new and useful Improvements in Base Tabletsfor Sound Records,

' whereof the following is a specification.

"shellac with'vegetable fibre. The suitability of this material is due to certain inherent properties permitting its useas a thermoplastic although it is. sufficiently hard to withstand the abrasive action of a reproducing needle.

Owing to the expense of this material,

efforts have been made to find a suitablematerial from which may be produced basetablets of suitable shape and thickness upon the surfaces of which may be placed a coating or facing of the same more expensive material commonly used for the production of the entire sound record. Under these circumstances, the sound record is im ressed upon the facing while the base-ta let is merely a vehicle for carrying the more expensive facing with the sound record impressed thereupon. In order, however, to successfully produce such a base-tablet it is necessary to obtain material having a combination of qualities diflicult to secure.

I have discovered a material which possesses the combination of strength, toughness, durability, resonance, melting point, co-eflicient of ex ansion, and ability to coalesce with or ad ere to the facing material which is required for successful use in manufacturing these base-tablets.

My invention consists of a bituminous material havin a high melting point intimate ly and evenly combined with a fibrous material.

According to my invention, I compressed bituminous tablet o roduce a suitable shape for receivin the required surfacing,

composed of a big melting int bituminous binder combined with a fi rous material such as asbestos fibre, cotton flock or the like thoroughly disintegrated and mixed by grinding withthe binder. This material is compressed as usual into a rigid tablet of substantiall the same size as the desired finished dis but slightly thinner, thus per- BASE TABLET FOB sounn nnconns.

' Application filed December 13, 1 921. Serial No. 522,128.

mitting the overlay of the facing of fibrated shellac or other mixture suitable .for record stock. p y

' For the fibrous material which enters into my improved base-tablet, I have found that it is necessary to employ a fibrous stock which is fairly free from non-fibrous particles. Asbestos fibre is very satisfactory. It is not afiected by the hi h temperature of the melting bitumen. referably longfibred asbestos stock should be chosen and disintegrated to the desired length rather than one of short. fibre, roduced directly from asbestos rock,which& have found usually contains an objectionable proportion of ground rock.

For the bituminous binder which is to be mixed with this fibrous material, I employ a hard bitumen, having a high melting point. It'may be made of certain grades of gilsonite, or else of certainother grades of gilsonite combined with sufficient softening material to produce a material possessing a melting proint within the limits of my 1nvention. or example, I may combine of ilsonite with 25% of a petroleum oil asp ialt having a melting int of 165 to 190 F. There is there y produced a bituminous binder having a melting point of not less than 250 F., and referably between 275 F., and 350 F. have found that if the binder has a meltin point substantiall less than 250 F., t e resulting base-tab et will not stand up under the temperatures encountered in t e subsequent manufacture of the completed record disk. On the other hand, if the binder has a melting oint of more than 350 F., the molding of t e tablet becomes diflicult or impossible owing to temperature and pressure requirements, but between the limits which I have named, the melting point may vary, de-

endent upon the temperatures avallable or moldi The m fiiod of compounding my ma terial is as follows:

From 20% to 45% of asbestos fibre, such 831 have described, disintegrated before or during the inding of the mixture, is mixed with 55% to of a bituminous binder made of a composition such as I have described, and lying between the limits of melting point which I have named. These two materials are ground together within, a suitable mill either ball or tube mill, until the mixture will all pass a may mesh sieve; This powder'ed mixture is then fused together on .a hot mixing'mill consisting of horizontal twin rolls steamheated, one of which rotates more rapidly tablets in amanner known in the art; The

either or both faces, an

blanksthus produced are heated on a steam table to a temperature of from 280 to 300 F., and placed in amold' of usual' desi and compressed. Instead of using a ie stamper in the mold, aplain steel surface is used, thus givin a perfectly plain .surface-to thetablet. an alternative method of procedure, the finely ground materials may under certain circumstances be fed directly to the heated molds and compressed into'the base-tablets. v Base-tablets, such as I have now: described, are. ready for fuse in the recordmaking industry, by subjecting them to'the known means for applyin record stock to impressing the record thereon.

Having thus described my invention, I

1 claim:

' 1. A base tablet for sound recordsfcomposed ofi 'an intimate and even admixture having a melting point'of not less'than 250 F., tough and strong, and adherent to an overlay of thermoplastic record material.

2. base-tablet for sound records coma melting1 tough an I lay of thermoplastic fibrated shellac.

posed of an intimate and even admixture of-asbestos with a bituminous binder having strong, and adherent to an over- 13. A base tablet for sound records composed of an intimate and "even admixture of fibrous material with a bituminous hard bitumen having a melting point lying between 275 and 350,F. f i

5. A base tablet for sound reproducing records composed of an intimate and even mixture of inorganic fibrous material with a bituminous binder, compressed to ensure rigidity, and adherent to an overlay of thermoplastic record'material. s 7 6. A, base tablet for sound reproducing records, composed of an intimate mixture of fibrous material and a bituminous binder composed of gilsonite and high melting pointpetroleum' oil asphalt in proportions to produce a mixture having a'melting point vof not less than 250 F., tou h andstrong, and adherent'to an I overlay o thermoplastic record material. a. a

In testimony whereof, I have hereunto signed my name at Maurer, N. this p second day of December, 1921. of fibrous material withabituminous binder JOHN STROTHER'MILLER, JR. I Witnesses: p I

, MICHAEL P. ENNIS,

WILLIAM FRANCIS KERWIN.

40 point of not less than 250 .F., 

